good points
my interpretation
the sonic devices are Heard by the dog
what the dog does next depends on their conditioning
the sound gets their attention, but what they do after that depends on whether the dog has learned that after the sound comes a treat, or some skunk piss
for the OP
I think adding a dog whistle and some treats (or skunk piss) to the walk,
could prove an interesting option to train the dog
I agree just blowing a whistle wont change the dogs behavior, its just a way to get his attention, and to train him to associate the sound with either a reward or a punishment